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Re: Electric Drive Question

A generator, batteries, solar panels, electric motor, a controller...
Why not just a little gas engine to a prop?
The only problem I can see is too much weight and too much money.
Other than that a 3 hp will move you along at half power at 3 knots.

Re: Electric Drive Question

Thanks for your thoughts Tom.
I'm sorry I did not state the proposed set up more. I will have the batteries and solar panels regardless of the aux power option.
The generator I have already. An outboard is an easy option but I wondered on the benefits of the electrical drive option.

Re: Electric Drive Question

Electric drive is quiet. Most trolling motors are designed for trolling, ie very slow. Ive read that model aircraft props can be substituted for the standard prop, which is supposed to fix that.Never tried it though. Also seen setups where the electric motor and prop are nicely encased in a flip up rudder, rather than just hanging a usually over length electric outboard off the back. Newer control systems are more efficient than the earlier versions. But I dont know any of the detail.

Re: Electric Drive Question

Hi nedL
My description is really bad, sorry. I listed the generator as an asset only, as a part that could be utilised if required for a proposed set-up.
I do intend to take the generator on board for protracted stays on the boat, primarily whilst at at anchor to charge the house batteries if required.
On a previous boat, a new Jeaneau 34 footer, I ran a 36inch screen TV, video player, electric kettle, micro wave etc. with a similar electrical set-up. My wife even took her hair dryer? I did not have a propane system on board.
The generator will be situated above decks to vent the exhaust whilst in use.
Whilst still in the pre-build stage I am considering an electrical drive system though the commercially available systems are extremely expensive when viewed against my intended hours of use.

Re: Electric Drive Question

I just finished building an 18' fantail launch and powered it with a 24 volt 80 lb. thrust trolling motor. With a three bladed trolling motor prop, it has a top speed of 5.5 mph. I've only been out a few times, but at top speed I can go a few miles and use up 20% of my battery. I've tried the model airplane props (post #4) and can get another .5 mph out of it, but with vibration. Plus, they are fragile.
I believe MiniKota has a 101 lb. thrust and also a 160 lb. thrust that attaches to an outboard.
Your cat should be an easy hull form to push through the water.

Re: Electric Drive Question

I have used an off the shelf electric trolling motor and dual purpose RV batteries to power a 20' keel sloop (one ton) a 24' light double end ketch (weight unknown, but probably similar) and a couple of dinghies. I probably never powered more than a mile, but one trip never killed even a single battery. I think the motor is 55lb thrust. It would not drive the keelboats into any significant breeze, but I only used it in a calm.
I suggest you look for a used trolling motor and try it out. A 20' cat should drive easily. Bring a long oar too.

Re: Electric Drive Question

I've been experimenting with a 55lb thrust trolling motor lately on a dinghy. A group 24 deep cycle lead acid battery (12V 85Ahr) seems to last about 45 minutes at full power. It will keep going but at a noticeable drop in power after that. That motor pushes my dinghy at just over 4 mph. The motor pulls 600 watts of power at full throttle, (12 volts @ 50 amps). That's 0.8 hp.
Pushing a 20 ft stitch and glue cat at 3 knots seems reasonable with this setup. With (2) batteries, you could expect about 1.5 hrs run-time using full throttle. That should be able to give you a 4-5 mile range (flat water, no current, no wind).
Travis.

Re: Electric Drive Question

I will second nedL's cautions on the generator. They can cause serious injury, illness, or death if not specifically set up for marine use. Check with Honda, but my understanding is they do NOT recommend their generators for boats. If you want to take along the generator, and use it ashore at your destination that is one thing. Using it aboard is a bad idea.

Re: Electric Drive Question

Out there in the real world many, many cruisers use small portable gas powered generators such as the Honda. Some store them below and bring up on deck for use. Some stow them on deck with a canvas cover. They are cheap, reliable, quiet, very little vibration, no installation cost, no through hulls. For most cruisers a heavy, expensive, hard to service, noisy complicated dedicated marine diesel genset makes no sense at all. Just sayin.

Re: Electric Drive Question

Thanks for all the comments and the heads up regarding safety and generators. There are risks attached to every item and activity, knowing the risks and using safe working practices can minimise most risks. I have used a Honda generator on board for over five years.
The petrol fuelled outboard has been ruled out, it will be the electric drive option for various reasons.
A motor in each hull with fixed props has been suggested which brings the option of a limited recharge of the batteries whilst sailing. The proposed motor supplier is to provide costs, weights and performance figures re thrust and recharge.

I will second nedL's cautions on the generator. They can cause serious injury, illness, or death if not specifically set up for marine use. Check with Honda, but my understanding is they do NOT recommend their generators for boats. If you want to take along the generator, and use it ashore at your destination that is one thing. Using it aboard is a bad idea.

Re: Electric Drive Question

Originally Posted by peb

What are the isdues with them that causes these problems?

Sent from my BLN-L24 using Tapatalk

Primarily carbon monoxide poisoning.
CO is hugely toxic, odorless and neutrally buoyant in air.
Our haemoglobin has a 250 times greater affinity for the CO molecule versus O2.
And with a half life of 5 - 6 hours, it's no wonder so many die from it.
Ventilate well and be sure the exhaust fumes are travelling away from your boat.
Know the signs and symptoms and beware.

Re: Electric Drive Question

Besides the CO2 issues Tom talks about, there are problems with the grounding of non-marine generators in a marine environment. This can cause electrocution, either on the boat or for people in the water in the vicinity of the boat. Like GrahamH mentions, there are risks with any activity, and boating has many inherent risks. I won't tell you not to use the Honda generator in this situation, but you should know the risks to yourself and others around you.

Re: Electric Drive Question

Have used a portable Honda generator on a 30 foot ex troller many times but yes some common sense is needed. Run the thing on deck not near any venting you may have. It takes for ever to burn a pint of gas so we're not talking about a lot of emission here just make sure it drifts away. The Honda's have thick rubber feet, on a wood boat not a concern for stray current IMO. Whether you're running 110 to the engine room or 12 volt or whatever for battery charging have good waterproof portable wiring (extension cord). We never used the thing steady for hours just a few hours here and there which sounds like all you need as well. For continuous use a little marine diesel unit would be the ticket.